[Feature]: Add Codeception configuration and some sample tests

[schmidt-travixmedia]

Feature description

It would be very helpful if a Codeception example configuration could be added, as it would be used in a real project. Tests should ideally be executed using a separate database that is reset after the tests. Example: A user registration is tested; then, a login with the newly registered user is tested. After running the tests, database should be reset so that the user does not exist in the database anymore.
The "Pimcore Skeleton" GitHub repository already brings a basic Codeception configuration, see pimcore/skeleton#109

[github-actions]

Thanks a lot for reporting the issue. We did not consider the issue as "Pimcore:Priority", "Pimcore:ToDo" or "Pimcore:Backlog", so we're not going to work on that anytime soon. Please create a pull request to fix the issue if this is a bug report. We'll then review it as quickly as possible. If you're interested in contributing a feature, please contact us first here before creating a pull request. We'll then decide whether we'd accept it or not. Thanks for your understanding.